Optical transmission system and optical amplifying apparatus optical amplifying unit and optical coupler for the same

摘要

PURPOSE: To obtain an optical amplifier system, etc., which can amplify signal light over a wide band and has satisfactory noise characteristic. CONSTITUTION: A signal light inputted to an amplifier system from an input terminal 11 is demultiplexed into a C-band signal light and an L-band signal light by means of an optical demultiplexing section 110, and the C-band signal light is amplified by means of an optical amplifier 2 for C-band. The L-band signal light is amplified by means of an optical amplifier 300 for L-band, after passing through an optical filter 120. The C-band signal light outputted from the amplifier 200 and the L-band signal light outputted from the amplifier 300 are multiplexed with each other by means of an optical multiplexer 400 and outputted from an output terminal 12. Since the reverse ASE light, which is generated when the amplifier 300 makes amplification is interrupted by the filter 120 and prevented from being inputted to the amplifier 200, the deterioration of the noise figure of the optical amplifier device is suppressed.